Though many possible remedies and folk cures have been suggested, there is no compelling evidence to suggest that any are effective for preventing or treating alcohol hangover.[4] Avoiding alcohol or drinking in moderation are the most effective ways to avoid a hangover.[4]
The socioeconomic consequences and health risks of alcohol hangover include workplace absenteeism, impaired job performance, reduced productivity and poor academic achievement. A hangover may also compromise potentially dangerous daily activities such as driving a car or operating heavy machinery.[5]

Contents

A painting from 1681 showing a person affected by nausea, a typical symptom of alcohol hangover

An alcohol hangover is associated with a variety of symptoms that may include drowsiness, headache, concentration problems, dry mouth, dizziness, gastrointestinal complaints, fatigue, sweating, nausea, hyper-excitability, anxiety, and a feeling of general discomfort that may last more than 24 hours.[6] Alcohol hangover symptoms develop when blood alcohol concentration falls considerably and peak when it returns to almost zero.[5][7] Hangover symptoms validated in controlled studies include general malaise, thirst, headache, feeling dizzy or faint, tiredness, loss of appetite, nausea, stomach ache, and feeling as though one's heart is racing. Some symptoms such as changes in sleep pattern and gastrointestinal distress are attributed to direct effects of the alcohol intoxication, or withdrawal symptoms.[8]Drowsiness and impaired cognitive function are the two dominant features of alcohol hangover.[7]

The processes which lead to hangovers are still poorly understood.[2] Several pathophysiological changes may give rise to the alcohol hangover including increased levels of acetaldehyde, hormonal alterations of the cytokine pathways and decrease of the availability of glucose. Additional associated phenomena are dehydration, metabolic acidosis, disturbed prostaglandin synthesis, increased cardiac output, vasodilation, sleep deprivation and insufficient eating.[1] Some complex organic molecules found in alcoholic beverages known as congeners may play an important role in producing hangover effects because some, such as methanol, are metabolized to the notably toxic substances formaldehyde and formic acid.[1]

Alcohol also induces the CYP2E1 enzyme, which metabolizes ethanol and other substances into more reactive toxins. In particular, in binge drinking the enzyme is activated and plays a role in creating a harmful condition known as oxidative stress which can lead to cell death.[10]

Acetaldehyde, the first by-product of ethanol, is between 10 and 30 times more toxic than alcohol itself[11] and can remain at an elevated plateau for many hours after initial ethanol consumption.[12] In addition, certain genetic factors can amplify the negative effects of acetaldehyde. For example, some people (predominantly East Asians) have a mutation in their alcohol dehydrogenasegene that makes this enzyme unusually fast at converting ethanol to acetaldehyde. In addition, about half of all East Asians convert acetaldehyde to acetic acid more slowly (via acetaldehyde dehydrogenase), causing a higher buildup of acetaldehyde than normally seen in other groups.[13] The high concentration of acetaldehyde causes the alcohol flush reaction, colloquially known as the "Asian Flush". Since the alcohol flush reaction is highly uncomfortable and the possibility of hangovers is immediate and severe, people with this gene variant are less likely to become alcoholics.[14][15]

In addition to ethanol and water, most alcoholic drinks also contain congeners, either as flavoring or as a by-product of fermentation and the wine aging process. While ethanol is by itself sufficient to produce most hangover effects, congeners may potentially aggravate hangover and other residual effects to some extent. Congeners include substances such as amines, amides, acetones, acetaldehydes, polyphenols, methanol, histamines, fusel oil, esters, furfural, and tannins, many but not all of which are toxic.[8] One study in mice indicates that fusel oil may have a mitigating effect on hangover symptoms,[19] while some whiskey congeners such as butanol protect the stomach against gastric mucosal damage in the rat.[20] Different types of alcoholic beverages contain different amounts of congeners. In general, dark liquors have a higher concentration while clear liquors have a lower concentration. Whereas vodka has virtually no more congeners than pure ethanol, bourbon has a total congener content 37 times higher than that found in vodka.[8]

Several studies have examined whether certain types of alcohol cause worse hangovers.[21][22][23][24] All four studies concluded that darker liquors, which have higher congeners, produced worse hangovers. One even showed that hangovers were worse and more frequent with darker liquors.[21] In a 2006 study, an average of 14 standard drinks (330 ml each) of beer was needed to produce a hangover, but only 7 to 8 drinks was required for wine or liquor (note that one standard drink has the same amount of alcohol regardless of type).[24] Another study ranked several drinks by their ability to cause a hangover as follows (from low to high): distilled ethanol diluted with fruit juice, beer, vodka, gin, white wine, whisky, rum, red wine and brandy.[23][24]

One potent congener is methanol. It is naturally formed in small quantities during fermentation and it can be accidentally concentrated by improper distillation techniques. Metabolism of methanol produces some extremely toxic compounds, such as formaldehyde and formic acid, which may play a role in the severity of hangover. Ethanol slows the conversion of methanol into its toxic metabolites so that most of the methanol can be excreted harmlessly in the breath and urine without forming its toxic metabolites. This may explain the temporary postponement of symptoms reported in the common remedy of drinking more alcohol to relieve hangover symptoms.[8][25] Since methanol metabolism is effectively inhibited by consumption of alcohol, methanol accumulates during drinking and only begins to be metabolized once ethanol has been cleared. This delayed action makes it an attractive candidate explanation for delayed post-intoxication symptoms and correlations between methanol concentrations and the presence of hangover symptoms that have been found in studies.[3]

Ethanol has a dehydrating effect by causing increased urine production (diuresis), which could cause thirst, dry mouth, dizziness and may lead to an electrolyte imbalance. Studies suggest that electrolyte changes play only a minor role in the genesis of the alcohol hangover and are caused by dehydration effects. Drinking water may help relieve symptoms as a result of dehydration but it is unlikely that rehydration significantly reduces the presence and severity of alcohol hangover.[3]
Alcohol's effect on the stomach lining can account for nausea because alcohol stimulates the production of hydrochloric acid in the stomach.

Studies show that alcohol hangover is associated with a decrease in blood glucose concentration (less than 70 ml/dl), but the relationship between blood glucose concentration and hangover severity is unclear.[3] Also known as insulin shock, hypoglycemia can lead to coma or even death.[26]

In current research, the significant relationship between immune factors and hangover severity is the most convincing among all factors so far studied.[3] An imbalance of the immune system, in particular of cytokine metabolism has been identified as playing a role in the pathophysiology of the hangover state. Especially the hangover symptoms nausea, headache, and fatigue have been suggested to be mediated by changes in the immune system. The concentration of several cytokines have been found to be significantly increased in the blood after alcohol consumption. These include interleukin 12 (IL-12), interferon gamma (IFNγ) and interleukin 10 (IL-10).[27] Some pharmacological studies such as on tolfenamic acid[28] and Opuntia ficus-indica (OFI)[29] have also indicated an involvement of the immune system. These studies suggest that the presence and severity of hangover symptoms can probably be reduced by administration of a cyclooxygenase inhibitor such as aspirin or ibuprofen.[3]

Several factors which do not in themselves cause alcohol hangover are known to influence its severity. These factors include personality, genetics, health status, age, sex, associated activities during drinking such as smoking, the use of other drugs, physical activity such as dancing, as well as sleep quality and duration.[3]

Genetics: alleles associated with aldehyde dehydrogenase (ALDH) and flushing phenotypes (alcohol flush reaction) in Asians are known genetic factors that influence alcohol tolerance and the development of hangover effects. Existing data shows that drinkers with genotypes known to lead to acetaldehyde accumulation are more susceptible to hangover effects.[30] The fact that about 25% of heavy drinkers claim that they have never had a hangover is also an indication that genetic variation plays a role in individual differences of hangover severity.[5]

Age: some people experience hangovers as getting worse as one ages. This is thought to be caused by declining supplies of alcohol dehydrogenase, the enzyme involved in metabolizing alcohol. Although it is actually unknown whether hangover symptoms and severity change with age, research shows that drinking patterns change across ages, and heavy drinking episodes that may result in hangover are much less often experienced as age increases.[5]

Sex: at the same number of drinks, women are more prone to hangover than men, and this is likely explained by sex differences in the pharmacokinetics of alcohol. Women attain a higher blood alcohol concentration (BAC) than men at the same number of drinks. At equivalent BACs, men and women appear to be indistinguishable with respect to most hangover effects.[30]

Cigarette smoking: acetaldehyde which is absorbed from cigarette smoking during alcohol consumption is regarded as a contributor to alcohol hangover symptoms.[10]

Hangovers are poorly understood from a medical point of view.[31] Health care professionals prefer to study alcohol abuse from a standpoint of treatment and prevention, and there is a view that the hangover provides a useful, natural and intrinsic disincentive to excessive drinking.[32]

Within the limited amount of serious study on the subject, there is debate about whether a hangover may be prevented or at least mitigated. There is also a vast body of folk medicine and simple quackery. A four-page literature review in the British Medical Journal concludes: "No compelling evidence exists to suggest that any conventional or complementary intervention is effective for preventing or treating alcohol hangover. The most effective way to avoid the symptoms of alcohol induced hangover is to avoid drinking."[4] Most remedies do not significantly reduce overall hangover severity. Some compounds reduce specific symptoms such as vomiting and headache, but are not effective in reducing other common hangover symptoms such as drowsiness and fatigue.[33]

Yeast-based extracts: The difference in the change for discomfort, restlessness, and impatience were statistically significant but no significant differences on blood chemistry parameters, blood alcohol or acetaldehyde concentrations have been found, and it did not significantly improve general well-being.[33]

Hair of the dog: The belief is that consumption of further alcohol after the onset of a hangover will relieve symptoms, based upon the theory that the hangover represents a form of alcohol withdrawal[32] and that by satiating the body's need for alcohol the symptoms will be relieved. Social drinkers and alcoholics claim that drinking more alcohol gives relief from hangover symptoms, but research shows that the use of alcohol as a hangover cure seems to predict current or future problem drinking and alcohol use disorder, through negative reinforcement and the development of physical dependence.[25][30] While the practice is popular in tradition[41] and promoted by many sellers of alcoholic beverages,[42] medical opinion holds that the practice merely postpones the symptoms, and courts addiction.[43] Favored choices include Fernet Branca[44] and Bloody Mary.[45]

Kudzu (Pueraria montana var. lobata): The main ingredient in remedies such as kakkonto. A study concluded, "The chronic usage of Pueraria lobata at times of high ethanol consumption, such as in hangover remedies, may predispose subjects to an increased risk of acetaldehyde-related neoplasm and pathology. ... Pueraria lobata appears to be an inappropriate herb for use in herbal hangover remedies as it is an inhibitor of ALDH2."[46]

Artichoke: Research shows that artichoke extract does not prevent the signs and symptoms of alcohol-induced hangover.[33]

Oxygen: There have been anecdotal reports from those with easy access to a breathing oxygen supply – medical staff, and military pilots — that oxygen can also reduce the symptoms of hangovers sometimes caused by alcohol consumption. The theory is that the increased oxygen flow resulting from oxygen therapy improves the metabolic rate, and thus increases the speed at which toxins are broken down.[48] However, one source states that (in an aviation context) oxygen has no effect on physical impairment caused by hangover.[49]

Fructose and glucose: Glucose and fructose significantly inhibit the metabolic changes produced by alcohol intoxication, nevertheless they have no significant effect on hangover severity.[33]

Vitamin B6: No effects on alcohol metabolism, peak blood alcohol and glucose concentrations have been found and psychomotor function is not significantly improved when using Vitamin B6 supplements.[33]

Alcohol hangover has considerable economic consequences. A British study found that alcohol use accounted for 3.3 billion (USD) in lost wages each year, as a result of work missed because of hangovers. In Canada 1.4 billion (USD) is lost each year because of decreased occupational productivity caused by hangover-like symptoms. In Finland, a country with a population of 5 million persons, over 1 million workdays are lost each year because of hangovers. The average annual opportunity cost due to hangovers are estimated as 2000 (USD) per working adult.[21] The socioeconomic implications of an alcohol hangover include workplace absenteeism, impaired job performance, reduced productivity and poor academic achievement. Potentially dangerous daily activities such as driving a car or operating heavy machinery are also negatively influenced.[5]

In mid-2017, it was reported that one company in the UK allows sick days when hung over.[52]

In 2012, Éduc'alcool, a Quebec-based non-profit organization that aims to educate the public on the responsible use of alcohol, published a report noting hangovers have long-lasting effects that inhibit the drinker's capabilities a full 24 hours after heavy drinking.[53]

In 2012, Las Vegas based Hangover Heaven, a mobile hangover treatment clinic, opened along with its Hangover Research Institute, which studies the treatment of hangovers.[54]